1. Field of the Invention
This invention relates to apparatus and a process for monitoring the quality of a suspension such as a slurry. Such monitoring may be for the purpose of determining the purity of the slurry, that is, the presence of foreign or adulterating particulate material and/or for determining the uniformity or constancy of the consistency of the slurry.
2. Prior Art
U.S. Pat. No. 4,758,308, issued Jul. 19, 1988, to Carr refers at column 2, lines 32 to 35 to a paper entitled "Detection and Quantification of Sticky Contaminants and Recycled Fiber Systems" by Doshi, Dyer and Krueger, stating at column 2, lines 52 to 58 that:
. . the sample of the pulp either directly or after concentration of the contaminants in a sample is formed into a hand sheet and allowed to dry for handling. The air dryed hand sheet is placed between appropriate filter paper and hot pressed to form a sheet in which the contaminants can be monitored. PA1 The patent art discloses photodetection monitoring means for particles detection of pulp. For example, U.S. Pat. Nos. 4,402,604 which issued Sep. 6, 1983 and 4,225,385 which issued Sep. 30 1980 disclose withdrawing of a sample of the pulp stock passing of the sample through a photoelectric detection system which detects the presence of dirt, shives and the like. U.S. Pat. No. 4,402,604 which issued Sep. 6, 1983 discloses a system whereby the liquid pulp or the pulp to be inspected is passed in a liquid state between a pair of transfer plates. The pulp is mixed with a pure liquid, that is, one without fiber content to control the consistency of the mixture as it passes through the plates. Light sources are applied to opposite sides of the moving sheet and a plurality of photosensitive devices are located in a row across the pipe to receive both reflected light and transmitted light. A series of photoelectric diodes are mounted across the plate to continuously scan the moving pulp. The output of each device is a signal dependent on the intensity of the light, and therefore the presence or absence of the particles. U.S. Pat. No. 4,225,385 discloses a method for directly passing of the pulp through a mixing unit for dilution of water and then through a inspection tube having a photoelectric device to scan the liquid as it passes through. Other patents have further considered analysis of the virgin pulp for foreign matter; for example, U.S. Pat. Nos. 4,184,204, 3,709,615, 4,318,180, 4,276,119, 4,441,960.
The Carr patent also discusses prior patents at column 1, lines 33 to 62 as follows:
Additional United States patents cited by the U.S. Patent and Trademark Office against the Carr application resulting in U.S. Pat. No. 4,758,308 include U.S. Pat. Nos. 4,342,618, 4,374,703, 4,504,016 and 4,514,257.